The HMG Box, a novel motif of minor-groove DNA recognition, defines a diverse class of nuclear proteins. Of particular importance in human biology are HMG transcription factors, which regulate essential functions in the immune system (lymphoid-specific regulators TCR1 and LEF1), metabolism (insulin-responsive transcription factor IREBP1), and male sexual developemnt (testis determining factor SRY). Here we propose to conduct multidimensional NMR studies of a specific complex between a representative HMG Box (SRY) and its DNA binding site. These studies will test the following hypotheses; Hypothesis 1. The sequence-specific HMG-Box exhibits a novel mechanism of DNA recognition. Hypothesis 2. On HMG binding, DNA undergoes a major structural change . Hypothesis 3. Mutation of conserved residues in the HMG Box alters protein structure, stability, or DNA-binding. Hypothesis 4. A common mechanism underlies both duplex DNA recognition and sequence-independent but structure-specific binding to 4-way DNA junctions. Structure-function relationships will be inferred from comparative NMR studies of SRY mutations associated with human developmental abnormalities. This application thus offers the exciting prospect of applying NMR to the molecular analysis of human genetic disorders.